On our May 2002 cruise, the shows were VERY cold. We had a light sweater for the ladies, and we needed it! The dining rooms weren't as bad, but still a bit chilly. I took the sweater every night. Sometimes we needed it, sometimes not. I'd say the WD theater was probably 65-70 on that trip and the dining rooms were 70-74? Outside temp probably average 85-88 this trip. We actually grabbed some towels off a housekeeping cart to wrap around us one time in the theater!
Our Jan 2003 Wonder cruise, the both the theaters and dining rooms were more like 70-74. The outside temperature for this trip was low 70s for a high.
I think that when it's hot during the day, the air conditioned spaces really crank out the cooling to compensate, then when evening comes, they're pretty cold. When the day time temps are lower, the air conditioned spaces are a little more consistent.
So I would highly recommend a light sweater for the ladies. If you don't use it, it won't take up much space. If you need it, you'll be glad you have it!